1. Field of the Invention
The present invention relates to a process and apparatus for etching an image within a solid article. More specifically, it relates to laser etching individual points of an image within the article to form the image.
2. The Prior Art
It is known that laser light interacts with opaque materials to alter the physical characteristics of the material. This phenomenon is utilized in various laser technologies, i.e., cutting, welding, drilling holes, and imprinting textures on the surface of materials. The U.S. patent to Sorkoram, U.S. Pat. No. 4,851,061, discloses a method and apparatus using a laser beam for cutting thermoplastic materials into different shapes. The U.S. patent to Macken, U.S. Pat. No. 4,458,133, discloses a laser apparatus for cutting sheets of material using templates.
Also known are materials which reflect laser light, for example, the U.S. patent to Nakamachi et al, U.S. Pat. No. 5,066,525, and the U.S. patent to Wood et al, U.S. Pat. No. 4,842,389, which disclose holographic heads-up displays. Also, it is known that laser beams travel through transparent materials, for example, lenses in laser systems, without interaction. However, if the concentration of laser radiation reaches a sufficiently high level, the transparent material may begin to break down, for example, when lenses in laser systems are damaged. Previous attempts have not been made to constructively utilize the interaction of laser beams with transparent materials.